This invention relates to surgical staplers for end-to-end anastomosis of tubular tissues such as bowel, bile ducts, and vascular arteries and veins, and more particularly to an improved stapler which considerably shortens the time and reduces the trauma of tubular tissue anastomosis, while improving the accuracy and reliability of the tissue stapling. Even more particularly this invention relates to an improved stapler which uses a novel, four piece disposable staple cartridge for holding the everted ends of the tissues, and the staples and trimming knives used to effect an end-to-end anastomosis.